This contractor acts as the data coordinator for the ultrasound B-scan assessment program by receiving, editing, storing, and analyzing data received from clinical and animal centers. The add-on to this contract requires that this same type of data coordination be extended to follow-up studies for about 489 patients. Analysis will include comparison of ultrasound, history, and angiographic findings obtained during initial and follow-up examinations. The principal objective is to assess how well ultrasound B-scan procedures can detect lesion changes in carotid arteries of patients in whom one carotid artery has had a clinically significant lesion.